If you're restoring a timber double hung window, the sash cord is the cheapest component in the whole job — and the one most likely to undo it. Here's how the main options compare, and why serious restorers keep coming back to one in particular.
Plain cotton cord
The traditional choice, and it looks the part. The problem is longevity: untreated cotton absorbs moisture and degrades in UV light. In the harsh Australian sun, plain cotton cords can rot and snap within just a few years — which means dismantling the window all over again.
Nylon and synthetic cords
Strong and weatherproof, but they look and feel wrong in a period window: shiny, slippery and unmistakably modern. Purely synthetic cords can also be too slick, letting knots slip, and they simply don't sit right with heritage joinery that's survived a century.
Waxed cotton with a concealed poly core — the best of both
This is the cord we supply at Sellaseal, and it's the one we'd fit in our own homes. On the outside: genuine waxed cotton, with the authentic look, matte finish and smooth pulley action of traditional cord. The wax coating resists moisture and reduces friction over the pulley wheel. On the inside: a hidden poly core that carries the load and shrugs off the UV degradation that destroys all-cotton cord.
From arm's length it's indistinguishable from the cord your window was born with — it just doesn't fail like it.
Made by people who've had 170 years of practice
Our 6mm waxed cotton sash cord is braided in Bolton, England by James Lever & Sons, a family rope-making firm founded in 1856 and now in its sixth generation. Their waxed sash cord has been the heritage restoration benchmark for generations — here's their remarkable story.
When a cord has been trusted on heritage windows for this long, the question really becomes: why would you fit anything else? Browse the James Lever & Sons heritage cordage collection.